1. Field of the Invention
The present invention relates to video graphics switchers. More specifically, the techniques of the present invention provide mechanisms for efficiently communicating characteristic information between display devices and hosts through a switcher.
2. Description of Related Art
Many conventional processing, multimedia, and control systems include a host connected to a display device. Any mechanism that operates as a source of video data is referred to herein as a host. Some examples of hosts include receivers, client computers, set top boxes, servers, etc. Any mechanism that visually presents the video data is referred to herein as a display device. Some of examples of display devices include monitors, displays such as flat panel displays or liquid crystal displays (LCDs), and projectors. Conventional systems provide somewhat limited mechanisms for hosts and displays to communicate information characterizing display devices and hosts, particularly when hosts and display devices are connected in more sophisticated arrangements through switching systems. Parameter or configuration information associated with a display device is referred to herein as information characterizing a display device or display device characteristic information. Examples of such information include resolution, vertical and horizontal frequency, aspect ratio, power management support, manufacturer code, etc. The information about the display device allows a host to more effectively use the display device.
In a simple case, a single host is a connected to a single display device. One technique that allows a host to determine characteristics of the display device involves connecting a predetermined number of pins to ground. Based on the number of pins connected to ground, a host could determine limited characteristic information associated with a display device. In another simple case, polarities associated with particular bits are flipped to communicate basic information. However, neither of these techniques could provide robust characteristic information.
The Extended Display Identification Data (EDID) format was developed by the Video Electronics Standards Association (VESA) to provide a data structure for a display device to communicate robust characteristic information to a host. The EDID structure allows a host and an associated graphics card to determine what type of display device the host is connected to. EDID includes parameters for communicating product serial numbers, video input types, maximum image sizes, phosphor or filter type, display gamma, chroma information, along with resolution, and frequency, etc.
However, mechanisms for communicating video graphic information such as EDID structures remain limited, particularly in video graphics switcher environments where multiple hosts can be dynamically connected to multiple display devices in a variety of arrangements. Consequently, the techniques of the present invention provide mechanisms for efficiently and intelligently communicating characteristic information in video graphics switcher environments.